Fellowships for radiology are generally not competitive. You will be fine going to USC for residency and returning to the east coast for a "good" fellowship.
With that being said, if your long term goal is to stay on the east coast for work, it makes sense to stick around for residency. Connections are the most important factor in the job hunt. Also, even though radiology residency is relatively less taxing compared to other specialties, do not discount how much it sucks having your family and support system far away during what will arguably be the hardest few years of your life.